It has long been known to use copy milling machines for cutting and shaping workpieces having complicated three-dimensional shapes. To this end, a model is mechanically scanned by means of a scanner or tracer head equipped with a stylus. During this scanning, the stylus is deflected. Signals corresponding to the size of the deflection are generated. A copy regulating means responds to these signals to generate feed signals for controlling the servodrives of the copy milling machine whereby the workpieces are cut and shaped.
Whereas previously analog contouring controls were used exclusively, digital contouring controls have come into wider use because digital controls can be used to reduce the relatively long machining times occurring during copy milling, thus producing a corresponding rise in productivity for such machines. This rise results from higher feed rates. However, additional problems arise when higher feed rates are used. It is very important that greater nominal deflections can be obtained with the stylus used. This permits larger lag distances avoiding an otherwise excessive control gain.
The aforementioned problems are well known, being described in the publications by S. Schreiber and U. Bruggemann "Design of a copying tracer head with large deflection range" and by R. Wollenberg, and R. Milnikel "Improvement of the dynamic response of copying heads with the aid of a microcomputer" in the Journal "Industrieanzeiger", No. 58 of 19.7.85.